"I told him he wasn't strong enough to go the other way," Reddick said.

Reddick has seldom been happier to have been proven wrong.

Donaldson delivered a monstrous and timely opposite-field home run with the bases loaded in the sixth inning, giving the A's all the runs they would get off White Sox ace Chris Sale in a 4-3 win.

That victory, coupled with Texas' 6-1 loss in Toronto, moved the A's into first place in the American League West by a half-game.

"JD has put us on his back," Reddick said, looking at Donaldson's team-best .329 average and 41 RBIs. "At some points, he's carried us."

The A's have won 18 of their last 21 games, including beating Sale twice. This is a left-hander who won 17 games last year and had a 28-inning scoreless streak before Donaldson's sacrifice fly against him Sunday in Oakland carried the A's to a 2-0 win.

In his last 361/3 innings against all comers, Sale has allowed five runs. Donaldson has driven in all five.

"He's one of the best left-handers in the league, if not the best," Donaldson said. He picked on a 1-1 fastball up and away and hit it the other way, just as Reddick suggested he couldn't.

"I wasn't trying to do too much," Donaldson said. "I'd already had two at-bats against him and was feeling very comfortable. He had to come in to me at that time, and I feel that any time a guy has to come at me, I'm going to be aggressive."

Being aggressive is second nature for Donaldson. He's now 10 for 18 when batting with the bases loaded. He wasn't necessarily supposed to be the A's cleanup hitter against left-handed pitching, but it's going to be difficult to get him out of that role. He's carrying a .350 average against left-handers, and five of his nine homers have come off left-handers.

"That was big-time stuff right there," manager Bob Melvin said. "He's got a consistent approach, and he understands what he has to do."

Before the Donaldson slam, the first of the year for the A's, the White Sox were able to gingerly build a 3-0 lead. The first of three hits for Tyler Flowers, a homer, was the first hit off Jarrod Parker in the third inning.

An inning later, the White Sox scored an unearned run on Dayan Viciedo's sacrifice fly, and in the fifth, Alejandro De Aza made it 3-0 with a sacrifice fly that followed hits by Gordon Beckham and Flowers. Parker was a little unlucky to give up three runs, but he held it there.

"He threw an 0-2 hanger (changeup) to Flowers, and we didn't make a play, and there was a bloop hit," Melvin said. "So it wasn't like he was getting knocked around."

After the Donaldson slam, Parker put up scoreless innings in the sixth and seventh.

Reddick's leap at the fence robbed Conor Gillaspie with one out in the ninth inning to preserve Parker's victory and Grant Balfour's 15th save.